type person = {
  name: string
  firend? : {
    name: string,
    age?: number,
    girlfirend?: {
      name: string
    }
  }
}
const info: person = {
  name: 'why',
  firend: {
    name: 'whya',
    age: 30,
    girlfirend: {
      name: 'lili'
    }
  }
}
console.log("info", info)
console.log(info.name)
console.log(info.firend?.name) // 可选链的使用
console.log(info.firend!.age)
console.log(info.firend?.girlfirend?.name)
export {}